It is well known that the halogenation of phenols and their ethers occurs essentially at the ortho and para positions relative to the phenol or phenol ether group. Substitution at the meta position by halogen is regarded as difficult and it is usually necessary to adopt indirect methods which involve a number of reaction steps and are therefore expensive. However, meta-bromophenols and their ethers are known to be useful products for the chemical industry, as they may be used, in particular, as intermediate products in the manufacture of bactericides and insecticides, in the preparation of resins by condensation with formaldehyde for providing a crease-resistant finish for textiles, and in the preparation of lubricants, hydraulic fluids, etc.
Recently, it has been shown by J. C. Jacquesy, M. P. Jouannetaud and S. Makani (J. CHEM. SOC., CHEM. COMM., 1980, 110-111) that bromination of para-cresols, 2,4- or 3,4-xylenols and the ethers thereof, in a superacidic medium (HF--SbF.sub.5), at low temperature (-45.degree. C.), leads to good yields of derivatives which are brominated at the meta position of the phenol or ether function. Under the conditions used by these authors, ordinary phenol and ortho- and meta-cresol essentially yield para-brominated derivatives. The article mentioned above also states that the formation of meta-brominated derivatives, in the case of the para-cresols and xylenols or their ethers, does not result from any isomerization of ortho- or para-brominated compounds since, for example, 2-bromo-4-methylphenol or 4-bromo-2,6-dimethylphenol or the ethers thereof are recovered unchanged when treated with a superacid HF--SbF.sub.5 at -45.degree. C.